On 2025-12-16 03:53, Alejandro Colomar wrote:
See the following program, to understand all the placements. I've used
attributes that don't make sense, to trigger diagnostics, which make it
more visible to what they apply.
alx@devuan:~/tmp$ cat attr.c
[[gnu::packed]] void f(void), g(void); // Attributed: f, g
void [[gnu::packed]] h(void); // Attributed: void
void i [[gnu::packed]](void); // Attributed: i
void j(void) [[gnu::packed]]; // Attributed: void(void)
[[pure]] enum a {A} v, vv; // Attributed: v, vv
enum [[pure]] b {B} w; // Attributed: enum b
enum c [[pure]] {C} x; // Syntax error
enum d {D} [[pure]] y; // I think this won't work.
enum e {E} z [[pure]], zz; // Attributed: z
These examples unfortunately confused me more than they helped. They
would be better if they used attributes that made sense for what's being
declared. For example:
enum d {D} [[pure]] y;
conforms to C23 and so "works" in some sense. However, GCC rightly
issues two warnings for it because it is dubious for one reason (the
[[pure]] applies to y's type, but not to enum d in general) and dubious
for another (types can't be pure).
Also, there are exceptions to the guidelines that you gave. For example,
"[[fallthrough]];" doesn't follow the guidelines.
